The present invention relates to a wrist watch including a can-shaped lower case portion in which a clockwork is received and a watch glass is pressed onto that lower case portion with interposition of a seal ring.
Various watch systems are known, in which individual components of the wrist watch are inserted from above into the lower case portion and the watch is locked by means of a bezel and/or the watch glass.
The German patent publication 24 52 479 discloses a watch case formed of one sheet of material. The watch glass in this instance is held in the case by means of a bezel, two fastening claws and two fastening supports. Each fastening support is provided at its lower end with a thread onto which a nut is screwed. The bottom and the bezel of the watch case are connected to each other by those nuts. The disadvantage of this watch case is that it contains too many structural parts and is therefore expensive in manufacturing. Furthermore, if a fastening of the watch strap to this watch case, by means of known spring webs, takes place these spring webs should be inserted between corresponding connecting strips formed on the lower portion of the watch case. A smooth, harmonic transition from the watch case to the watch strap is then impossible.
German Offenlegunsschrifts 30 43 263 and 31 16 306 disclose a wrist watch which is comprised of relatively few simple structural components and in which due to the specific structure of the fastening arrangement for the watch strap a harmonic watch unit is formed. However, in these known constructions the screwed-on bezel is still utilized to ensure the proper holding of the watch strap.
Watch cases have been known, in which the watch glass has been connected immediately to the case without the use of a bezel. Such a watch case has been described, for example in German Offenlegunsschrift 28 36 827. The watch case shown in this German publication is a completely closed box which has on the front side thereof only a narrow opening which serves as a passage for the hour and second hand shafts. The watch glass in this watch covers the entire front side of the case box and is connected to the case box by screws. The watch strap is fastened to the case in the known fashion by means of connecting webs or strips projected outwardly from the case at two opposite sides thereof so that a clearance between the case and the watch strap is formed whereby the case does not harmonically merge into the strap.
Still another structure of the watch case has been known, in which the upper frame of the case which receives the clockwork and supporting the glass, has laterally projected flanges, on each of which a web rests, forming one portion of the watch strap, and in which those flanges lie on the bottom portion of the case and are connected thereto by bolts, screws or rivets. Such a structure is described in German Offenlegunsschrift 27 33 094. The disadvantage of this known construction is that the webs, proposed in the fastening arrangement for the watch strap are, at least partly, surrounded by the strap formed of leather, plastics or textile material, or, in case of a metal or link strap, should be connected to the strap by pins, screws, rivets or bolts. This requires additional manufacturing steps so that the cost of the watch is increased. Furthermore, the provision of the upper frame of the case with two flanges in which cheeks are formed and on which the end portions of the watch strap are laid from above and providing various bores for receiving fastening screws and pins as well as recesses for necessary seals, makes the manufacturing very complex and troublesome so that the watch altogether is expensive and its manufacturing is inefficient.
Usually plastic glass or mineral glass is utilized for manufacturing watch glasses. In the case of wrist watches of the higher price range often a watch glass made of sapphire glass is used for reasons of its durability. In order to improve an aesthetic appearance of the watch and provide for greater design possibilities the watch glasses have been partially metallized or covered with a contrast material.
The above mentioned glass materials, however, have some disadvantages. Plastics glass is very soft so that it soon becomes scratched and thereby loses nice appearance and satisfactory optical visibility. Mineral glass is substantially harder and durable but the wearing properties of this glass are not completely satisfactory. Sapphire glass has proved to have specifically high resistance to scratching and durability but it is relatively expensive.